Abstract Cold roll-forming is a process of forming metal from sheet, strip or coiled stock into shapes of essentially uniform cross-section by feeding the strips through successive pairs of rolls arranged in tandem. The deformation in cold roll-forming is quite complex and due to this inherent complexity of the process, the roll design and other decision-makings often involve a good deal of trial and error. The “forming angle” method, which is regarded as reasonably dependable for assisting in determination of the number of roll stations to form a bend, takes account of the intermittent deformation under each roll station only in a crude way. The present paper describes a method which predicts the deformation length under each roll station a priori by minimizing the deformation energy and assuming the material to be rigid-plastic. The theoretical results have been verified by roll forming channel sections from mild steel and aluminium strips and the agreement between the theory and the experiment has been found to be extremely good. The results also suggest that the deformation length depends on the physical parameters of the produced channel section but is practically independent of the mechanical properties of the workmaterial for the situations considered in the present investigation.